Engine oil is also used for micro-sealing between pistons, piston rings and cylinder walls, as there is always a gap of a few microns between these parts. Thanks to the additional sealing action of the oil, the high gas pressure resulting from combustion is transferred without loss to the piston crown and converted into kinetic energy. In this way, optimum engine power is achieved.
Another function of engine oil is to provide additional engine cooling. When fuel is burned, only a quarter of the released energy can be used to move forward, part of the energy leaves the engine with exhaust gases, the rest of the heat energy must be removed by the coolant and engine oil. So, for example, the piston can only be cooled by engine oil. On the one hand, the heat from the pistons is transferred through the piston rings and sealing oil to the working surfaces of the cylinders, then to the coolant. On the other hand, the oil sprayed into the crankcase directly cools the pistons. Accordingly, each bearing of the crankshaft, camshaft, etc. cooled by the flow of oil passing through it. The heat accumulated by the engine oil is transferred through the walls of the oil pan to the air flow around it.
Multigrade oils
Modern oils are lubricants refined from petroleum. But, before a lubricant refined from petroleum turns into motor oil, oil manufacturers add special additives to it, which at the end of the production process make up to 20% of the oil formulation.
Additives protect the oil from oxidation and prevent the formation of foam at high engine speeds. One of the most important additives are viscosity index improvers, which are long molecular chains that swell when heated and contract again when cooled. These additives act in such a way that the oil adjusts to the temperature regime of the engine and covers several viscosity classes at once. These additives also have a negative property: at high temperatures, they lose most of their properties. In addition, water, fuel and combustion residues set a limit on the life of an engine oil. Mineral oil does not withstand the pressures and temperatures prevailing in the engine for long enough. Therefore, regular oil changes are not a luxury that you can refuse, but a necessary standard to ensure the normal and long-term operation of your engine.
Synthetic oils
Synthetic oils are considered the most expensive, as they are partially composed of artificial chemical compounds of carbon, hydrogen and oxygen. In this case, only those molecules are selected that can optimally perform the required lubrication tasks. In practice, this means that these oils age much more slowly than mineral oils. They also evaporate more slowly and have a high long-term stability, which means that they retain their original high viscosity grade for a long time.
Purchasing engine oil
For the engine of your Fiesta car, regular multigrade oil will do. It is only important that the oil complies with all existing standards. In case of doubt, find out the information you are interested in from the seller, not paying much attention to the powerful advertising campaign of the oil manufacturer. Only the oil specification, the correct viscosity grade and the text printed on the packaging indicate the applicability of the oil.
Pic. 5.2. The range of use of engine oils of various viscosities in gasoline engines depending on the outside temperature
Ford recommends SAE 5W-30 engine oils (for diesel engine SAE 10W-40), that meet the ACEA specification A1-96, B-96 or Ford specification WSS-M2C912-A1 (for ACEA A3-96, V3-96 diesel engine) (pic. 5.2, 5.3). If you wish to use another oil, it must be of API SH quality for gasoline engines (for diesel engines CC MC G5, PD2, API SH). Oils with an API designation of SC, SD, SE, or SF can even interfere with the normal operation of your engine. If the oil meets the above criteria, oils from different manufacturers can be mixed with each other. You only have to consider that the special qualities of previous formulations may deteriorate over time. Each type of oil is distinguished by a special formulation of additives, the effect of which, when mixed with other oils, may deteriorate. For this reason, mixing mineral and synthetic oils is also not beneficial.
Pic. 5.3. The range of use of engine oils of various viscosities in diesel engines depending on the outside temperature
TECHNICAL DICTIONARY
Basic concepts. Oil classification systems
Viscosity.
This is a value for determining the fluidity of the oil. In winter, the engine oil must be so thin that, after starting a cold engine, it immediately gets to all lubrication points. On the contrary, in summer it is necessary to use a thick oil so that the oil film does not break at high temperatures.
SAE (Society of Automotive Engineers).
The fluidity of an oil is indicated by the viscosity grade. The corresponding classes are established by the American Institute of the Society of Automotive Engineers (SAE), e.g. SAE 5W-30. The lower the first number, the easier the oil flows at low temperatures (W - winter). Oil 0W flows at a temperature of -30°C, at 5W this figure increases to -25°C, at 15 W - up to -15°C. The higher the second number, the better the oil resists high temperatures.
ASEA (Association des Constructeurs Européen d'Automobiles).
Introduced in 1996, the European standard for oil, which replaced the CCMS standard. For gasoline engines there are groups A1 (not containing rectified alcohol), A2 (with a low content of rectified alcohol) and A3 (energy saving oil). For diesel engines, oils are divided into groups B1, B2 and B3.
SSMS (Comitté des Constructeurs d'Automobiles du Marché Commun).
The specification consists of letters «G» (petrol) And «PD» (diesel) and numbers. The higher the number, the better the quality of the oil.
API (American Petroleum Institute).
The specification consists of a letter «S» (Gas engine) or «WITH» (diesel engine), as well as the subsequent letter. The further the letter is in the alphabet, the better the quality of the oil.
For this reason, you should not mix pure diesel oils with gasoline engine oils, in the worst case, you will cause serious damage to your engine.
Fiesta gasoline engines do not require the use of expensive synthetic oil. Ford recommends using SAE 5W-30 viscosity grade oil in our latitudes (see fig. 5.2).
Oil consumption
If your Fiesta engine is in excellent technical condition, you should add a small amount of oil at the prescribed oil change intervals (0.25–0.5 l), and the diesel engine is no exception. This rule is valid for all engines only if you regularly change the oil and your engine is not overloaded by excessively harsh, sporty driving. Any engine uses some oil. Part of the engine oil burns out during engine operation, which is normal. Leaky places in the engine, damaged timing gaskets, worn oil scraper rings, too large clearances between the pistons and cylinder surfaces, or too large clearance between the valve guides and valve stems will dramatically increase normal oil consumption.
Blue exhaust plume - indicator of wear
By looking at the blue exhaust plume, you can directly identify one of the many engine faults. Even when the oil level remains unchanged, this does not indicate a normal engine condition: excess fuel and condensed water dilute the oil, which leads to a deterioration in its lubricating properties. This phenomenon is observed primarily in winter and when driving short distances - the engine rarely reaches its operating temperature, and the moisture does not have time to evaporate from the oil. In this case, it is necessary to change the oil at shorter intervals: after 6000 km of run or once every six months.
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